Dalila Espírito-Santo

Epigenetic rather than genetic factors may explain phenotypic divergence between coastal populations of diploid and tetraploid Limonium spp. (Plumbaginaceae) in Portugal

BackgroundThe genus Limonium Miller comprises annual and perennial halophytes that can produce sexual and/or asexual seeds (apomixis). Genetic and epigenetic (DNA methylation) variation patterns were investigated in populations of three phenotypically similar putative sexual diploid species (L. nydeggeri, L. ovalifolium, L. lanceolatum), one sexual tetraploid species (L. vulgare) and two apomict tetraploid species thought to be related (L. dodartii, L. multiflorum). The extent of morphological differentiation between these species was assessed using ten diagnostic morphometric characters.ResultsA discriminant analysis using the morphometric variables reliably assigns individuals into their respective species groups. We found that only modest genetic and epigenetic differentiation was revealed between species by Methylation Sensitive Amplification Polymorphism (MSAP). However, whilst there was little separation possible between ploidy levels on the basis of genetic profiles, there was clear and pronounced interploidy discrimination on the basis of epigenetic profiles. Here we investigate the relative contribution of genetic and epigenetic factors in explaining the complex phenotypic variability seen in problematic taxonomic groups such as Limonium that operate both apomixis and sexual modes of reproduction.ConclusionsOur results suggest that epigenetic variation might be one of the drivers of the phenotypic divergence between diploid and tetraploid taxa and discuss that intergenome silencing offers a plausible mechanistic explanation for the observed phenotypic divergence between these microspecies. These results also suggest that epigenetic profiling offer an additional tool to infer ploidy level in stored specimens and that stable epigenetic change may play an important role in apomict evolution and species recognition.

Warm-Temperate Forests of Central Portugal: A Mosaic of Syntaxa

Despite extensive afforestations with allochthonous tree species, the Atlantic facade of the mountain chain that extends through central Portugal still presents several examples of autochthonous forests that show significant floristic and ecophysiological diversity. Along a N-S transect of no more than 100 km along this range, zonal forest types may vary from semi-deciduous Quercus robur formations with evergreen understory (Viburnum tinus or Arbutus unedo) to marcescent Quercus broteroi forests and sclerophyllous forests of Quercus suber. Adding further diversity to the vegetated landscape are extrazonal groves of non-sclerophyllous evergreens like Prunus lusitanica, Ilex aquifolium, Rhododendron ponticum, Laurus nobilis and Myrica faya, relicts of the Tertiary laurisilva. While data suggest that a macrobioclimatic gradient (from temperate to mediterranean) may be responsible for such a variety of forest formations, a convoluted set of orographic, edaphic, hydrologic, microclimatic and paleohistorical factors certainly contributes to explain the variation in this peculiar region. This study compares these plant communities of central Portugal, classified according to Braun-Blanquet methodology. We studied the number of relict species present in each community, as well as the laurophyllous taxa that had become adapted to the present climatic conditions. Extrazonal groves showed the greatest percentage cover by relict species, while zonal forests contained more newly adapted laurophyll species. Among the zonal forests, those dominated by Quercus robur in warmer areas had the highest percentage covers of relict species. Finally, we propose the new syntaxon Asparago aphylli-Quercetum suberis lauretosum nobilis.